TCP-ETX: A cross layer path metric for TCP optimization in wireless networks

Transmission Control Protocol (TCP) suffers degradation in wireless networks because, among other factors, low quality links tend to interrup a TCP connection. Most of the routing protocols use the number of hops as path metric without considering the link condition. Expected Transmission Count (ETX) calculates the estimated number of transmissions to successfully transmit a packet, but it fails to calculate the correct number of transmissions for a TCP segment. In addition, the overhead of ETX is very high because it needs to probe all destinations to calculate the link loss probability. In this paper, we propose a novel cross layer path metric, TCP-ETX, which calculates the accurate number of transmissions for TCP segments and minimizes the protocol overhead. To evaluate our proposal, we conduct simulations and compare our solution to existing protocols, which shows that our protocol can offer a significant improvement on the TCP performance.